In this chapter, we begin with a discussion of motivation itself, and use that discussion to sketch four possible theories of distinctively moral motivation: caricature versions of familiar instrumentalist, cognitivist, sentimentalist, and personalist theories about morally worthy motivation. To test these theories, we turn to a wealth of scientific, particularly neuroscientific, evidence. Our conclusions are that (1) although the scientific evidence does not at present mandate a unique philosophical conclusion, it does present formidable obstacles to a number of popular philosophical approaches, and (2) theories of morally worthy motivation that best fit the current scientific picture are ones that owe much more to Hume or Aristotle than to Kant.